Airplane propeller



L. M. HAMILTON AIRPLANE PROPELLER Filed March 18, 1940 INVENTOR. MI 2. TO N Lsus M.

, Patented Dec. 2, 1941 UNl'iED ,STATES PATENT orrlca AIRPLANE PROPELLEB Leslie M. Hamilton, Monroe Township, Delaware. County, Ind.

Application March 18, 1940, Serial hlc. 324,556

3 Claims. (01. no -1oz) elevation.

Figure 6 is an enlarged horizontal cross sec-.

'Whereas propellers have heretofore been de-- vised wherein the hub structure of the propeller has embodied opposed radial sockets in which the blades are movably seated and so retained, that by the eifect'of centrifugal force they are automatically shifted from a given pitch position, and which said blades, in the absence of said centrifugal force, are automatically returned to their initial positions, I am not aware that any construction based uponthe aforesaid general principle has even been developed whereby the above named advantages are possible in a propeller device which is intended especially, as in the present instance, for an airplane of the miniature or model type.

To provide a propeller embodying the above named general principles, and especially intended for model, airplanes, which will be of relatively light weight, capable of economical manufacture, adapted to convenient handling in merchandising, and which is durable, dependable, and easy to install, .is the object, broadly stated, of my invention. This general object, as well as other and more specific aims of the invention, are accomplished by, and my invention is embodied in the new construction, combination and arrangement of parts illustrated in' the accompanying drawing and described in the following specification.

In the several views in the drawing, the difler-' ent parts of the invention are identified by suitable characters of reference applied to them in the views, in which Figure 1 is a side view' of my improved propeller, showing the appearance and position of the blades when the latter are in full feathered position and whenthe propeller is static. v b

Figure 2 is a front view, taken in the direction of arrow 2 inFigure 1.

Figure 3 is a front view of the propeller, showing the appearance and posltion of the blades when the latter are in the pulling position, and

when the propeller'is in action.

Figure 4 is an enlarged horizontal cross section view, on the broken line H and as seen in the direction of arrow 4 in Figure 1.

Figure 5 is a vertical central sectional view as ,seen in the direction of arrow I in Figure 4, por

. D of predetermined length and which is provided tions of the bases of the blades .being shown in .of arrow 9 in Figure 8, a portion of one of the blade receiving socketsbeing broken away.

My invention provides a hub structure and blades so coordinated therewith that the blades at such time as the engine is not running, are in the full feathered position (both in line with the longitudinal aixs of the plane) but which said blades will, shortly after the engine will have started, automatically assume and will continue in pulling position, but which said blades will, when the engine stops, automatically return to the original or full feathered position. In the present illustration the propeller is about fourteen inches in length over all and its weight is approximately two ounces.

The hub, made of cast metal, preferably an aluminum alloy, consists of a body structure A which is provided witha transverse bore B, and axial bore C. A quota of air-craft steel tubing near each of its'ends with opposed apertures E and E, and at its central portion with a transverse bore F of same diameter as the axial bore C of the said hub, is fitted metal to metal within the aforesaid bore B of said hub. A tubular section G is then inserted into the bore 0 of said hub and through the bore F of said maintubing D and it constitutes a member which, besides beingadapted to receive the spindle I of the driving shaft 2, constitutes a structural stay to interlock the hub structure and the main tubing section D into integrated relation. The free portions of said tubing D constitute diametric socketsH and H.

The inboard portion or base J of each of the blades I, which said blades are madeof woodor of suitable light plastic, is provided with a central bore K and is invested with a light metal cylindrical band designated as a bushing L which is of external diameter to be slidingly re-.

ceived in the aforesaid socket. This bushing is made fast to the base of the blade, as by cross pins M and N.

At a point a predetermined distance from the outboard end of the base of the blade, is a diametric aperture 0 through said bushing and in the direction of 'about seventy-five degrees.

2 the base. Extending from the ends of this aperture at the opposite sides of the bushing, are spiral slots P and P in opposed directions, and which are formed in the base the present instance, measured on a plane at a right angle to the axis of the thimble, is It will be understood that the degree of sweep (which determines the pitch of the blades) may be varied according to ditferentiations in reference to power and capacity of motors, and in differences in dimensions and cambers of blades.

Within the aforesaid Q of predetermined length and capacity. A cross pin R serves to retain this spring, and also it serves as an abutment against which the spring exerts a pressure, as will be presently described. On the other end of said spring is a bearing cap having rounded head portion S.

The blade is now disposed with its bushing L inserted into the socket H of the hub structure, and it is turned until the aperture is in registration with the apertures E and E. A cross pin T is now inserted into an aperture E, passed through aperture 0 and through the other aperture E; the tapered end T' riding on the rounded head S of the bearing cap of the said spring Q. Now by applying said cross pin is held against dislodgement and the installation of the blade will have been completed. The manner of installing the other blade is of course the same as above described. The action of the spring Q which is. now under compressive urge, between the abutment member or crossrod R of the blade, and the cross pin T of the socket, is to urge the blade inwardly, or toward the axis of the hub, the spiral apertures P and P acting (when there is absence of centrifugal force) to move the blades rotatively and to the full feathered position as shown in Figure 1. The cross pin T holds the blade and its bushing L in assembly with the hub structure D and H and shaft'2 and as the blades move outward due to centrifugal force, or inward due to the action of spring Q, the spiral slots P, in moving over the said cross pin T, cause the blade to change its pitch.

On the rear face of the hub is cemented a layer of emery cloth V which afiords a tight engagement with the head end of the. driving shaft, when the binding nut 3 is tightened. It will be observed that by my new construction all compression strains which are incident to integrating the hub structure with the driving shaft are taken substantially by the tubular section G and the hub structure proper, thereby assuring against any distortion of the tubing that constitutes the sockets, and providing dependably free action of the blade bases in the said sockets. The hub structure is adapted, as shown in the drawing, to have applied to its frontal portion the snap-on spinner W made of stamping of aluminum alloy, and of formation to complete the streamlining of the propeller.

A propeller constructed in accordance with bore K is a helical spring of the blade and in the said bushing. The sweep of said slots in or nature of siderable. Any modification incident to variation of length of blades, or the degrees of pitch or camber do not involve any structural changes.

It will be understood that modifications in the several structural features of the invention may be made, without departing from the spirit the invention, and I wish the invention to be construed asof the scope defined in the appended claims.

What I claim as my invention, is:

1. A propeller of the kind described, comprising a hub structure embodying radial sockets a cotter pin U, the

each having a cylindrical bore and being provided with opposed apertures in the walls of said sockets, blades, each having its base of diameter to slidingly engage the bore of said socket and being provided with an axial bore, and there being similar opposed spiral slots in the walls of said base and an abutment member at the inboard'end of said axial bore, a helical spring within said axial bore and which rests upon said abutment member, and a cross pin passed through the apertures of the said socket, thereby uniting the base with the socket and depressing the spring whereby the blade is urged to full feathered status in inboard position.

2. A propeller of the kind described, comprising a steel tubular body section having a central transverse bore and being provided with opposed apertures spaced from' its ends, a hub structure integrated with said body section at 4 its central portion and having an axial bore my invention gives effective performance, pulling needed. Its weight, approximately two ounces,

as hereinbefore stated, for a fourteen inch propeller, is only slightly more than the weight of an ordinary all-wood propeller, and is incona of said socket to correspond with the said transverse bore of said body section, a tubing inserted through said axial bore and said transverse bore and which is integrated with the said hub structure, blades, each having its base of diameter to be received and retained slidingly within the opposed portions of the said body section and being provided with a central longitudinal bore, and there being similar opposed spiral slots in the walls of said base, an abutment member at the inboard end of said longitudinal bore, a helical spring within said longitudinal bore and which rests upon said abutment member, and a cross pin passed through the apertures of said body section and engaging said spiral slots thereby uniting the blade base with the body section and depressing the spring whereby the blade is urged to full feathered status in the inboard position.

3. Model airplane propeller construction comprising a hub structure embodying diametric opposed sockets each having a cylindrical bore and being provided with diametrically opposed apertures adjacent to the outboard end thereof, a blade for each socket, each of said blades having its base portion sheathed with a cylindrical bushing of diameter to slidingly engage the bore and being provided with a central axial cavity of predetermined length at whose outboard end a diametric aperture extends through the walls of said bushing, and there being similar opposed spiral guideways extending from the ends of said aperture, a helical spring within said cavity and having a rounded cap integrated with its outboard end, a rod extending across said cavity at its inboard end, and a cross pin passed through the apertures of said socket and the diametric aperture of the said blade base, and there retained, thereby uniting said blade with the? said socket and engaging and depressing the said spring, whereby the blade 5 urged to full feathered status in inboard posi- LESLIE M. HAMILTON. 

